Starting apparatus for electric discharge devices



; 10, 1933. LPH 1,930,083

STARTING APPARATUS FOR ELECTRIC DISCHARGE DEVICES Filed Oct. 3, 1928 INW Patented Oct. 10, 1933 r UNITED STATES" PATENT; OFFICE STARTINGAPPARATUS FOR ELECTRIC DISCHARGE DEVICES Application October 3, 1928.Serial No. 310,057

10 Claims. (01. 176-124) The present invention relates to dischargedevices, and particularly to gas or vapor discharge devices whichoperate with a hot cathode.

The particular object of the invention is to improve the starting andoperation of such devices, but various other objects and advantages willbe obvious from the following particular description of an apparatusembodying the invention or from an inspection of the accompanyingdrawing. The invention consists in certain new and useful features ofconstruction and combinations of parts hereinafter set forth andclaimed.

Gas or vapor discharge devices are commonly provided with means forimpressing a high voltage of short duration upon their electrodes inorder to induce a discharge when starting, and also in some cases havemeans for heating the cathode in order to facilitate starting. In such'cases the application of the high potential to the electrodes before thecathode has had time to heat up is injurious, as, if a discharge isstarted before the cathode has reached the proper temperature for freeemission of electrons, the 25 -discharge is confined to one spot on thecathode, and tends to disintegrate the electron emitting material. Thepresent invention is for an apparatus to delay the initial applicationof the high potential until a suitable interval for cathode heating haselapsed, said apparatus offering the advantage that it is simple andrapidly resets itself for a new cycle of operation, even while thedischarge device itself is operating.

In the accompanying drawing there is shown 35 for purposesofillustration one form of apparatus embodying the invention, in whichFig. 1 is a schematic diagram of a discharge device and its connectionto the associated apparatus,

Fig. 2 is a front elevation of a thermal delay mechanism which may beemployed, and

Fig. 3 is a sectional view taken on the line 33 of Fig. 2.

In the drawings a transformer 1 is either directly or inductivelyconnected to a source of alternating current. The discharge device 2 hastwo anodes 3 and 4 at one end which are respectively connected throughballast resistances 5 and 6 and leads 7 and 8 to opposite ends of saidtransformer 1. A cylindrical cathode 9, which is preferably of metalcoated with barium oxide, but may be made of any material which freelyemits electrons when in a heated condition or which is coated therewith,is located at the op- 5 posite end of said discharge device, and isconed to lead 10 at a point exterior to the discharge device, thence bysaid lead 10 and said cathode 9 to the other end of said resistance 13.A mercury switch 17, of a type commonly referred to as a shifter, hasone terminal connected to said lead 10, and the other terminal isconnected through resistance 27, lead 18, resistance 19 and lead 20 tolead 7. A bimetallic strip 21 is connected to one end of said resistance19 and is adapted to curl into contact with a contact point 22 connectedto the opposite end of said resistance 19 under the influence of theh'eat generated by resistance 19 when current is passed through it.

Figs. 2 and 3 show a preferred arrangement of thethermostatic element. Ayoke 23 of porcelain or other insulating material at one end carries anend of the bimetallic strip 21, supporting it over an opening in saidyoke which allows free access of air for cooling after operation. Theresistance 19, which is on the order of 2000 ohms, is wound upon thestrip 21, and has one end connected thereto. Lead 20 thus makes contactwith both through the terminal 24. The other end of the resistance 19 isconnected to the terminal 25 by means of a flexible lead 28. Saidterminal also carries the contact point 22, extending into the centralopening in the yoke 23 in which the bimetallic strip 21 freely moves,and adapted to make contact with a contact point 26 on the bimetallicstrip 21 when said strip has been heated to a desired amount.

As is usual in circuits for discharge devices of this type the shifter17 (which is only schematically shown) is normally in a circuit closingposition, but has an armature in electromagnetic relation to the core ofchoke coil 11, so that when the current through said choke coil 11 is ofthe value which normally flows through said coil in operation of thedevice the armature is 05 attracted to said core and rotates saidshifter to a circuit opening position. In the usual circuit prior tothis invention the current flow through said choke coil 11, shifter 17and resistance 27 (the resistance 19 not being heretofore used) was 11sufficient to operate said shifter to an open position, thus producing avoltage surge on the electrodes of the discharge device, immediatelyupon application of electrical potential to the energizing transformer.But according to the present invention the resistance 19 is inserted,its resistance being so large that the shifter is not actuated to anopen position until the thermostatic element 21 has short circuited saidresistance 19 under the influence of the heat given off from saidresistance, the time interval for which operation is so adjusted as toallow suflicient heating of the cathode, being on the order of 45seconds. As soon as the resistance 19 has been short eircuited a largercurrent flows through the choke coil 11, thus attracting the armature ofthe shifter 17 and rotating it to the open circuit position, andallowing the choke 11 to produce a voltage surge on the terminals of thedischarge device 2, the shifter 17 again closing the circuit as themagnetic field around choke 11 collapses (unless a discharge is set upwithin the discharge device) allowing recurrent voltage surges, once thecathode is hot, until the discharge is initiated, in the manner wellknown to the art. As soon as shifter 17 opens the circuit the bimetallicelement 21 starts to cool, in order to be ready for starting the lampagain, but it has sufiicient thermal capacity to remain closed forseveral seconds. allowing a number of current surges, if necessary tostart the discharge, before again inserting the resistance.

It is to be understood that the discharge device 2 may be filled withany desired gas such as neon, or source of vapor such as mercury,although for certain purposes a mixture of gases such as helium and neonmay be used.

It is also to be understood that the structure shown and described isfor purposes of illustration only, and that the invention can beembodied in other forms without departing from the spirit thereof. It isobvious that other forms of delay devices could be substituted for mythermal device, and that the invention is applicable to direct currentas well as alternating current discharge devices.

I claim:

,1. In combination with a gaseous discharge device having a thermioniccathode adapted to give off electrons when heated, means for heatingsaid cathode to a temperature at which the free electron emissiontherefrom will support the normal discharge current, means for supplyinga voltage surge to said discharge device. and means for delaying saidvoltage surge until said cathode has reached said discharge supportingelectron emitting condition.

2. In combination with a gaseous discharge device having a thermioniccathode adapted to give off electrons when heated, means for heatingsaid cathode to a temperature at which the free electron emissiontherefrom will support the normal discharge current, means forinitiating a discharge within said device, and means comprising athermally controlled switch for delaying the operation of said means forinitiating a discharge until said cathode has reached an operatingdischarge supporting electron emitting condition.

3. In combination with a gaseous discharge device having a thermioniccathode adapted to give off electrons when heated, means for heatingsaid cathode to a temperature at which the free electron emissiontherefrom will support the normal discharge current, means for applyinga voltage surge to said device and means comprising a thermallycontrolled switch for delaying said voltage surge until said cathode hasreached said tdischarge supporting electron emitting condiion.

4. In combination with a gaseous discharge device having a thermioniccathode adapted to give off electrons when heated, means for heatingsaid cathode to a temperature at which the free electron emissiontherefrom will support the normal discharge current, means for applyinga voltage surge to said device comprising an inductance and a switch inparallel with a discharge path, and means for delaying the discharge ofsaid inductance until said cathode has reached said discharge supportingelectron emitting condition.

5. In combination with a gaseous discharge device having a cathodeadapted to give olT electrons when heated, means for heating saidcathode, means for initiating a discharge within said device, means fordelaying the operation of said means for initiating the discharge untilsaid cathode has reached an operating temperature, and means toautomatically reset said delaying means upon initiation of the dischargethrough said device.

6. In combination with a gaseous discharge device having a cathodeadapted to give off electrons when heated, means for heating saidcathode, a means for supplying a voltage surge to said discharge device,a means for delaying said voltage surge until said cathode has reachedan operating temperature, and means to automatically reset said delayingmeans upon initiation of the discharge through said device.

7. The method of starting a gaseous discharge device having a thermioniccathode adapted to give off electrons when heated, comprising heatingsaid cathode to a temperature at which the free electron emissiontherefrom will support the normal discharge current, and applying 8.voltage surge to said device after said cathode has reached saiddischarge supporting electron emitting condition.

8. In combination with a discharge device having a thermionic cathodeadapted to give off electrons when heated, means for heating saidcathode to a temperature at which the free electron emission therefromwill support the normal discharge current, means for initiating adischarge within said device, and means for delaying the operation ofsaid means for initiating a discharge until said cathode has reachedsaid discharge supporting electron emitting condition.

9. The method of starting a discharge device having a thermionic cathodeadapted to give off electrons when heated, comprising heating saidcathode and initiating the discharge through said device after saidcathode has reached said discharge supporting electron emittingcondition.

10. In combination, an electric gaseous discharge device having athermionic cathode, means to heat said cathode to a temperature at whichthe free electron emission ,therefrom will support the normal dischargecurrent, means for initiating a discharge within said device, and meansto prevent hot spotting of said cathode comprising means for delayingthe operation of said means for initiating a discharge until saidcathode has reached said temperature.

LEROY J. BUT'I'OLPH.

CERTIFICATE or CORRECTION.

Patent No. 1,930,033. October 10', 1933.

LERQX J. .BUTIOLRH,

It is hereby certi'fied' that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,line 67, claim 2, for "an operating" read said; and line 133, claim 9,after "cathode" insert the words to a temperature at which the freeelectron emission therefrom will support the normal discharge-current;and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 28th day of November, A.- D. 1933.

F. M. Hopkins I (Seal) Acting Commissioner of Patents,

